Many different types of lumbar contour mechanisms are provided, both in a manual and power version. One such manual version is shown in U.S. Pat. No. 5,775,773, which shows a plurality of horizontally extending lumbar members which are attached to transversely spaced vertical holding mechanisms, whereby the vertical holding mechanisms can be bowden from top to bottom by way of a linkage, together with a bowden cable which, when shortened, changes the convexity of the lumbar mechanism. As the lumbar mechanism is positioned in a seat back, the seat back also conforms to the shape of the lumbar contour mechanism and therefore changes the contour of the seat back. Typically a manual handle is connected to the opposite end of the bowden cable and is routed to a position, for example, either adjacent an edge of the seat back or an edge of the seat bottom, whereby rotation of the handle causes the convexity of the contour mechanism.
Power versions also are provided, where the convexity is changed by way of a power system of sorts, such as an electric motor, which also forms a bowing or convexity to a lumbar mechanism. It is also common to have both a two-way mechanism, that is, where the mechanism is movable in two contour directions, that is, to increase and/or decrease the convexity, as well as a four-way power lumbar system, that is, where the convexity of the lumbar mechanism can be changed in both directions, as well as the actual vertical position of the lumbar mechanism itself relative to the seat back can be changed in two directions.
Various different designs exist for such a device. First, some designs have air bladders which inflate to provide an enlarged volume at the lumbar to support the person's back. Other designs include a flexible plate, whereby the ends of the plate can be moved together to change the convexity of the plate and thereby change the convexity of the seat back.
One such design for a deformable plate is shown in U.S. Pat. Nos. 5,335,965 and 5,567,011 (incorporated herein by reference). Such a plate is shown where a pair of threaded rods are threaded into a cylindrical scroll such that turning the scroll threads the threaded rods into and out of the scroll. Numerous shortcomings exist with this prior design. First, as the threaded rods thread into both ends, the amount of change in elongation of the threaded rods is limited by somewhat less than the length of the cylindrical scroll, as the threaded rods will thread into the scroll and abut at the minimum position, and some thread length must be left in the scroll to hold the rods. Secondly, this also requires that the torque on the scroll be relatively high as two rods are being threaded into the scroll at the same time. Thus, the power required to turn the scroll is also relatively high in the case of a powered lumbar because the linear displacement over time is twice that of a single rod. Nor is it satisfactory to simply change the thread size of the threaded rods so as to decrease the linear displacement over time, as the threaded rods are preferably of a molded plastic material and therefore small threads could not withstand the force on the plastic threads. Finally, as designed, it is difficult to provide a power source to the central scroll as it is intended for the scroll to turn relative to the threaded rods, and torque applied to the scroll causes a moment in the opposite direction as well.
The objects of the invention are therefore to overcome the shortcomings and impediments of the prior art device.